1. Metabolism & Enzymes
What term describes all the chemical reactions that occur in an organism?
Metabolism
What process maintains relatively stable internal conditions in an organism?
Homeostasis
Which type of membrane transport does not require the cell to supply energy: passive or active transport?
Passive transport.
During diffusion, what is the direction of net particle movement: high to low concentration or low to high concentration?
High to low concentration.
Which tiny air sacs in the lungs are the main site of gas exchange?
Alveoli.
What is the main role of enzymes in metabolic reactions?
Enzymes speed up reactions by lowering the activation energy needed. They are not used up in the reaction.
When someone becomes too hot, they sweat. How does sweating help regulate body temperature?
Sweat evaporates from the skin, removing heat and cooling the body.
A cell moves a substance from a lower concentration to a higher concentration using a membrane pump. Identify the transport process and its energy requirement.
Active transport. Moving against the concentration gradient requires energy; ATP powers the pump in this example.
What is the name for the net movement of water across a selectively permeable membrane?
Osmosis
At the lungs, in which direction does each gas move: oxygen and carbon dioxide?
Oxygen moves from the alveoli into the blood; carbon dioxide moves from the blood into the alveoli.
Building a protein from amino acids and breaking down glucose are metabolic processes. Which is anabolic, and which is catabolic?
Building a protein is anabolic; breaking down glucose is catabolic.
On a cold morning, someone starts shivering. Explain how this response helps maintain homeostasis.
Shivering involves rapid muscle contractions that generate heat.
A molecule moves from high to low concentration through a membrane protein without using ATP. What specific type of transport is this?
Facilitated diffusion.
A membrane allows water to pass but prevents sugar from crossing. Side A has a dilute sugar solution, while Side B has a concentrated sugar solution. In which direction will water move overall? Explain.
Water moves overall from A to B, toward the more concentrated sugar solution.
Why does oxygen move from the alveoli into the blood without requiring ATP for the crossing itself?
Oxygen crosses by diffusion, moving down its partial-pressure gradient from alveolar air into incoming blood. This crossing does not require ATP.
An enzyme works well at normal body temperature but loses activity at a much higher temperature. Explain what may have happened to its structure.
The enzyme may have denatured. Its shape, including its active site, changed, so the substrate no longer fits properly.
A student says, “Homeostasis means body conditions never change.” Correct this statement using body temperature as an example.
Internal conditions fluctuate within a suitable range. For example, temperature may rise during exercise, triggering responses that bring it back toward its usual level.
A cell’s ATP supply suddenly drops. Which is more likely to be affected first: an ATP-powered ion pump or oxygen moving directly through the membrane?
The ATP-powered pump is affected first because it depends directly on ATP.
Oxygen can continue diffusing down its concentration gradient without ATP.
A red blood cell is placed in a solution with a much higher concentration of nonpenetrating solutes. Predict what happens to the cell and explain why.
Water leaves the cell by osmosis, causing it to shrink.
Alveoli have thin walls, a large total surface area, and a rich capillary supply.
So, Thin walls shorten the diffusion distance, and the capillary supply brings incoming blood and carries oxygenated blood away! True or False.
TRUE Thin walls: shorten the diffusion distance. Large surface area: allows more gas to cross at once. Capillary supply: brings incoming blood and carries oxygenated blood away, helping maintain gradients. Accept any two explained features.
Nutrients alone cannot replace the enzyme’s function. Without the functioning enzyme, that reaction may proceed too slowly to meet the cell’s energy needs.
After running on a hot day, a student has lost water through sweating. Explain how sweating and thirst work together to maintain homeostasis, and identify a problem if the student does not replace the lost water.
After running on a hot day, a student has lost water through sweating. Explain how sweating and thirst work together to maintain homeostasis, and identify a problem if the student does not replace the lost water.
Sweating helps ________________ while Thirst requires ________________
Sweating helps cool the body, while thirst encourages water intake to replace losses. Without replacement, dehydration can reduce the body’s ability to cool itself and maintain normal function.
A cell contains a higher concentration of an ion than its surroundings, BUT it continues taking in that ion. A student claims, “It must be facilitated diffusion because a protein is involved.” Is it true or false?
The claim is incorrect or false! A transport protein can participate in either process. Because the ion moves from lower to higher concentration, this is active transport, requiring an energy source.
Two sides of a membrane have equal concentrations of a substance that can cross freely. A student says, “Diffusion has stopped because the concentrations are equal.” Is the student correct?
The student is incorrect. Particles continue moving in both directions, but equal amounts cross each way, so there is no net movement. This is dynamic equilibrium.
A person’s lungs exchange gases normally, but their heart pumps too little blood during exercise. Explain why their muscles may still receive insufficient oxygen and how this affects aerobic ATP production.
Gas exchange loads oxygen into blood, but circulation must deliver that blood to muscles. Reduced blood flow limits oxygen delivery, reducing the muscles’ ability to produce ATP through aerobic respiration.